ATA transport experiment: Triple slit emittance selector data

A common element to most of the ATA transport experiments was a measurement of the beam's phase space properties. In general, we wanted a diagnostic that would quickly give us the time-resolved information that would quantitatively tell us how much of an effect a given ''knob'' or new machine element had on the beam's brightness. As explained below, it is extremely difficult to make quantitative measurements of the brightness of an ion-focused beam while it is still on the channel, nor is simple, unimpeded vacuum expansion much better. Instead, we designed and installed a simple set of three range-thick apertures beyond the fusible link which allowed us to use beam bugs to measure J over a useful range of nearly two orders of magnitude. Our results showed that the peak brightness of the beam core is a 10-15 ns spike whose temporal position follows the timing of the laser pulse and whose magnitude and duration is relatively insensitive to beam current, benzene pressure, laser intensity, profile, or timing. 2 figs., 1 tab.